The invention relates to a circuit arrangement for the filling or refilling, as required, of a storage tank with liquid, such as water, and more particularly for filling a carbonating tank in a beverage dispenser, wherein carbonated liquid is withdrawn in measured quantities from the storage tank during a dispensing mode and wherein replenishment is controlled by an electronic circuit including a flow-rate control unit which is responsive to water-requirement level values as provided by an electronic sensor.
It is common practice, for example to produce blended beverages, shortly before consumption, by using a variable mixture consisting of soda water and beverage concentrates. To prepare this soda water, a storage tank, preferably chilled, is employed in a manner known to those skilled in the art and quantities of soda water are withdrawn, as required, from the storage tank to prepare the blended beverages. The ingredients for the soda water, i.e., CO.sub.2 gas and fresh water, are periodically supplied to the storage tank according to the amount of soda water withdrawn. To supply CO.sub.2 gas to the storage tank, a CO.sub.2 supply cylinder is connected thereto via a pressure-reducing valve. To fill and refill the storage tank with fresh water, the tank is connected to a water supply line. This water supply line is connected to a common water supply source or the water can be delivered from a water tank. A flow input regulator controls the water intake required in each case according to the soda water level in the storage tank. The soda water level is read by sensors which, in the interest of a simple design and simple signal processing, comprises a series-connected measuring circuit. If an adequate water pressure is present in the supply line, the input regulator for the fresh water is simply constructed by using an electrically triggered valve system. However, if one cannot assume with certainty that a sufficient water presssure will always be available in the supply line, it is often necessary to provide a pump unit in conjunction with an appropriate valve system. The water supply pressure must be sufficiently high, because the water--at least during the filling of the storage tank--must be supplied against the high pressure of the CO.sub.2 gas.
Functional units, such as triggerable valves as well as pump units, are to a large extent subject to extremely high loads during turn-on or turn-off. Especially if these operating cycles are up against relatively short delivery or dead times, these functional parts are subject to considerable wear. Also unnecessary and disturbing operating cycles of the flow-rate control units can result, particularly in connection with the refilling, because the surface of the soda water is also moved up and down in the area of the water-level sensor.
The primary object of the invention, therefore, is to reduce the switching frequency for the flow-rate control unit by extending the filling time period by a predetermined amount to permit the liquid level to rise above a predetermined level so that the volume of the gaseous head space and pressure within a carbonator tank is maintained substantially constant. It might be possible to use water-level sensors that act upon sensitive switches. This would enable the attainment of the desired overlap. However, such systems are expensive to produce. In addition, special care must be exercised with respect to their operability, and the various moving parts must be continuously monitored so as to insure that they are fully operable. Thus, in the case of the system advocated by the invention, one need not rely on such techniques. Rather, a circuit arrangement is disclosed that senses the water-requirement level value by a single electrode and generate a water demand signal when the level falls below a first predetermined level that energizes supply means, controlled by timer means, that permits the water to rise to a second predetermined level above the first predetermined level resulting in substantial reduction, if not elimination, in refill short cycling of the equipment as well as maintaining the above mentioned substantially constant gaseous head space and pressure within the carbonator tank.